An Al alloy (specific resistance of roughly 3.0 μΩ·cm) has conventionally been used as the wiring material for a semiconductor device. However, pursuant to the miniaturization of wirings, a copper wiring with lower resistance (specific resistance of roughly 2.0 μΩ·cm) has been put into practical application. As the process for forming a copper wiring, generally adopted is the method of forming a diffusion barrier layer made of Ta or TaN on a wiring or a wiring groove, and thereafter subjecting copper to sputter deposition. High purity copper of 5N to 6N is normally produced by performing wet or dry purification to electrolytic copper having a purity level of 4N (excluding gas components) as the crude metal, and this has been used as a sputtering target.
As described above, while copper is extremely effective as a wiring for semiconductors, copper itself is an extremely active metal and diffuses easily, and there is a problem in that copper contaminates the Si substrate or its periphery through the semiconductor Si substrate or the insulator film formed thereon. In particular, pursuant to the miniaturization of wirings, it is no longer sufficient to merely form a conventional Ta or TaN diffusion barrier layer, and improvements in the copper wiring material itself are demanded. Thus, previously, proposed as the copper wiring material was a copper alloy comprising a self-diffusion suppression function which is realized by adding manganese (Mn) to copper (Cu), and reacting the Mn in the Cu—Mn alloy with the oxygen of the insulator film to self-form a barrier layer.
Examples of a Cu—Mn alloy sputtering target are listed below.
Patent Document 1 describes a sputtering target containing 0.1 to 20.0 at % of Mn and remainder being Cu, wherein concentration of unavoidable impurity elements of which the diffusion coefficient is smaller than the self-diffusion coefficient of Cu is 0.05 at % or less.
Patent Document 2 describes a sputtering target containing 0.1 to 1.0 atomic percent of B as an additive element, further containing 0.1 to 2.0 atomic percent of Mn and/or Ni, and remainder being Cu and unavoidable impurities.
Patent Document 3 describes a sputtering target containing 0.1 to 1.0 atomic percent of B as an additive element, further containing 0.1 to 2.0 atomic percent of elements (including Mn) that develop a compound with B, and the remainder being Cu and unavoidable impurities.
Patent Document 4 describes a sputtering target containing one or more components selected from a group of V, Nb, Fe, Co, Ni, Zn, and Mg and one or more components selected from a group of Sc, Al, Y, and Cr so that the total content thereof becomes 0.005 to 0.5 mass percent, further containing 0.1 to 5 ppm of oxygen, and the remainder being Cu and unavoidable impurities.
Patent Document 5 describes a sputtering target containing more than 6 to 20 mole percent of oxygen, further containing one or more types among Mo, Mn, Ca, Zn, Ni, Ti, Al, Mg and Fe in a total amount of 0.2 to 5 mole percent, and the remainder being Cu and unavoidable impurities.
Patent Document 6 describes a sintered sputtering target material formed from metal powder of Mn, B, Bi or Ge and alloy powder or sintered metal containing X (including Cu) and Y, wherein the material contains 50% or more of crystal grains having an average grain size of 0.1 to 300 μm, and the gas content is 600 ppm or less.
Patent Document 7 describes a sputtering target for inhibiting the generation of particles, wherein the sputtering target contains 0.6 to 30 mass percent of Mn, 40 ppm or less of metal-based impurities, 10 ppm or less of oxygen, 5 ppm or less of nitrogen, 5 ppm or less of hydrogen, 10 ppm or less of carbon, and the remainder being Cu.
In addition, as a wiring material for semiconductor devices proposed by the present Applicant, described is a sputtering target for forming a copper alloy wiring for semiconductors, wherein the material contains 0.05 to 5 wt % of Mn, the total content of one or more elements selected from Sb, Zr, Ti, Cr, Ag, Au, Cd, In, and As is 10 wtppm or less, and the remainder is Cu (refer to Patent Document 8).
Moreover, the present Applicant has previously disclosed a copper alloy wiring material for semiconductors made from a Cu—Mn alloy (refer to Patent Document 9), and in particular proposed a sputtering target, wherein the target contains 0.05 to 20 wt % of Mn, the total content of Be, B, Mg, Al, Si, Ca, Ba, La, and Ce is 500 wtppm or less, and the remainder is Cu and unavoidable impurities.
A copper-manganese alloy sputtering target for use in the foregoing copper alloy wiring and the like for semiconductors aims to improve the performance of the thin film mainly with additive elements.
Generally speaking, upon preparing a target, a copper-manganese alloy ingot obtained through melting and casting is processed into a target shape of a predetermined size, and the surface is thereafter cut to obtain the target. In the foregoing case, the machinability of the target material is an important factor. This is because, since the target is cut and subsequently polished to obtain the ultimate surface form, if the cutting is insufficient, cutting marks will remain on the surface, and it is not possible to obtain the smoothness of the target surface.
When the smoothness of the target surface is improved, it is possible to inhibit the generation of particles during sputtering, and form a thin film with superior uniformity. Nevertheless, the conventional technologies did not develop the target material from this kind of perspective.
Patent Document 1: Japanese Patent No. 4065959
Patent Document 2: JP-A-2009-97085
Patent Document 3: JP-A-2010-248619
Patent Document 4: JP-A-2002-294437
Patent Document 5: JP-A-2008-311283
Patent Document 6: JP-A-2009-74127
Patent Document 7: JP-A-2007-51351
Patent Document 8: JP-A-2006-73863
Patent Document 9: International Publication No. 2008/041535